1. Field of the Invention
The present invention relates to the field of Quantum electronics, and more particularly to lasers that can be widely used as a powerful tool for solving problems in various fields of science and technology, such as--laser spectroscopy, photochemistry, photobiology, medicine, optical telecommunication, color television, color microscopy, color holography, information coding, and technology control.
Primarily, the invention can be used in cases when polychromatic laser emission with a pre-assigned oscillation spectrum is required, for example, continuum spectrum, multicolor sections of continuum spectrum or multicomponent linear spectrum with required spectral distribution of lasing power.
2. Description of the Prior Art
There is known a method for superbroadband or control generation spectrum lasing [A. G. Zhiglinskiy, A. M. Izmailov "Device for coherent electromagnetic radiation" Russian patent No. 4318986 issued Sep. 21, 1987], where definite sections of the active medium, corresponding to the pre-assigned wavelengths of laser oscillation (superbroadband continuum is a particular case of a control oscillation spectrum lasing), are simultaneously pumped. The pre-assigned wavelength radiations are chosen from the radiation of the fixed sections of active medium and simultaneously directed together with stimulated radiation of the pre-assigned wavelengths at their own (for each wavelength) pumped sections of active medium.
There is a laser realizing this method (see FIG. 1 ) and containing: pump system, active medium (AM) (solution of organic dye) and a resonator, consisting, in it's turn, of a dispersive element (D), operating in an autocollimation regime, two achromatic objectives (O.sub.1 and O.sub.2) and a highly reflective mirror M.sub.1. The first objective is optically connected with the dispersive element, it being known that the active medium is placed in it's focal plane. The second objective O.sub.2 is placed from another side of the active medium, being optically connected with a highly reflective mirror M.sub.1. The distances between the mirror M.sub.1 and the active medium AM, between the active medium AM and the second objective O.sub.2 are selected so that the objective O.sub.2 reflects the active medium on a working surface of the mirror M.sub.1. The described laser works as follows. In accordance with the pre-assigned spectrum of laser emission, sections of the active medium to be pumped are defined. These sections are defined in the focal plane of the first objective, according to dispersion of the selective element (D). The defined sections of the active medium are pumped by the radiation of the pumping system. Spontaneous radiation, emitted by the pumped sections of the active medium arrive at the objective O.sub.l and, in a parallel pencil of rays, is directed to the dispersive element D. After autocollimation reflection the radiation returns to the appropriate sections of the active medium AM, being amplified there. Then the second objective O.sub.2 focuses this radiation on the end mirror M.sub.1 and, after reflection, this radiation is focused again into the same pumped zones of the active medium.
There is known another laser [A. G. Zhiglinskiy, A. M. Izmailov "Laser with a control generation spectrum and spectral component brightness regulation" Russian patent No. 4867886 issued Oct. 2, 1990, and A. G. Zhiglinskiy, A. M. Izmailov "Controlled spectrum generation laser" U.S. patent application Ser. No. 07/483112 filed Feb. 21, 1991.] (see FIG. 2), realizing this known method and comprising an active media AM with broadband luminescent spectra (solutions of organic ayes), a dispersive element D (diffraction grating), resonator mirror M.sub.1 and a lens, to be installed between the dispersive element D and the active media AM and, at last,--a device PL for AM pumping. This pumping device PL pumps different sections of the active media, lying on various distances from the resonator optical axis. Spontaneous emission (and after following passages--induced radiation) from this section is reflected by mirror M.sub.1 back to the pumped sections and is amplified there. Between the mirror M.sub.1 and the interresonant lens L radiation is parallel to the optical axis. After refraction on the lens L the radiation is directed towards the grating D under various angles. The condition of the autocollimation reflections from the grating D for the radiation, emitted by various sections of the active media AM, will be fulfilled for the various wavelength. The radiation of this wavelength, after diffraction on the grating D, returns back to the pumped sections and is amplified there.
The main shortcoming of this previously used approach and associated lasers is the fact that these lamers can operate only with an active media having a so called plane configuration, because all the defined and pumped sections or zones of active media AM.sub.1, AM.sub.2, AM.sub.3, etc. should be placed in one plane--focal plane--of the first objective O.sub.1 see FIG. 1). This requirement significantly restricts the selection of the active media (only highly concentrated dyes are suitable) and eliminates the opportunity vf using volumetric active elements having a length along the resonator's optical axis. These aforementioned active media (mostly solid state--with a broadband emission spectra) are widespread, reliable, easy to handle and can provide high output power laser emission. Additionally, local pumping is principally impossible in many cases, for example, in chemical and gas lasers with electron or electrical pumping, solid state or dye lasers with flashlamp pumping.
There is a second important shortcoming in the described above lasers. Besides modes with the pre-assigned wavelengths there simultaneously appear a large quantity of secondary parasitic modes, propagating under various angles to the resonator axis, passing through two or more pumped zones of the active medium, providing competition with the main modes and decreasing the range of broadband oscillation.
Besides, the described lasers exhibit very high angle divergency of it's output oscillation.